1. Field of Invention
The present invention relates to a foaming mold using hollow tubes, and more particularly, to an improved mold for use in manufacturing a foamed product through foaming (or expansion molding), in which gas generated from the foamed product during the foaming can be smoothly discharged to the outside, thereby improving the quality of the final foamed product.
2. Description of the Prior Art
Generally, a foamed product is a product having a specific configuration desired by an operator, which is obtained by injecting a liquid foaming material into a mold having a cavity engraved in conformity with the desired configuration, and foaming and curing the liquid foaming material within the mold. The curing of the liquid foaming material into the foamed product can proceed or be facilitated by maintaining an atmosphere for the liquid foaming material within a specific temperature range or by adding chemical additives to the liquid foaming material.
Further, as for such a foamed product, it is possible to obtain a molded product comprising only a foam made through the curing of a liquid foaming material by filling a mold with only the liquid foaming material, curing the liquid foaming material and removing the mold. Alternatively, it is also possible to obtain a molded product into which a skin, a core and a foam such as a urethane pad made through the curing of a liquid foaming material are integrally incorporated by stacking the skin and core in a mold, filling the liquid foaming material between the skin and the core and curing the liquid foaming material.
Particularly, a vehicle instrument panel is a typical example of a molded product comprising a skin, a core and a foam pad as in the latter.
To produce such a molded product comprising a foam, when a liquid foaming material is injected into a mold, a sealing structure capable of preventing the leakage of the injected liquid foaming material from the mold is further required. Further, in order to obtain a good quality of a molded product comprising a foam made through foaming, there is a need for a degassing process by which gas generated while a liquid foaming material is cured into the foam during the foaming is discharged to the outside of the mold.
FIG. 1 is a sectional view showing a conventional foaming mold, and FIG. 2 is a sectional view illustrating a degassing process in the conventional foaming mold.
As shown in FIGS. 1 and 2, the conventional foaming mold comprises a mold unit 10 including separate first and second half molds 11 and 12 with inner cavities engraved in conformity with the configuration of a molded product 30; and a resilient sealing projection 20 fixed between the first and second half molds 11 and 12 of the mold unit 10 to enclose an outer periphery of the configuration of the molded product 30.
As shown in FIG. 1, the conventional foaming mold thus constructed is provided with the mold unit 10 including the first and second half molds 11 and 12 that have the cavities engraved in conformity with the configuration of the molded product 30 and are stacked one above another. Between the first and second half molds 11 and 12, the resilient sealing projection 20 having a circular cross section, for example, is fixed to and protrudes from one of the half molds while enclosing the outer periphery of the configuration of the molded product 30. Accordingly, when a liquid foaming material is injected into the mold unit 10, the foaming material is prevented from leaking out from the mold unit 10.
In order to produce the final molded product 30 comprising the skin 31, the core 32 and the pad 33 through the foaming using the conventional foaming mold described above, the core 32 and the skin 31 are stacked one above another between the first and second half molds 11 and 12, a liquid foaming material such as urethane is injected and cured between the core 32 and the skin 31, and the injected foaming material is molded into the pad 33 as a foam. Thus, the pad 33 is integrally combined with the core 32 and the skin 31 to form the final molded product 30.
Thus, a manufacturer can obtain the final molded product 30 comprising the foam having a desired configuration by means of the mold unit 10 provided with the sealing projection 20.
In performing the foaming using the conventional foaming mold, the degassing process of discharging gas, which is generated from the foam upon curing the liquid foaming material, to the outside of the mold is required during the foaming in order to prevent the deterioration of the quality of the product due to the presence of the remaining gas in the molded product 30, as shown in FIG. 2.
However, since the conventional foaming mold is not provided with an additional means for discharging the gas generated from the foam to the outside of the mold, the gas is discharged from the foam merely by causing two half molds to be spaced apart by a predetermined distance from each other. If the degassing is performed over an entire surface of the foam in such a manner at once, there are problems in that the efficiency of degassing is lowered and thus the quality of the foam is not uniform, whereby the resultant quality of the final molded product is deteriorated.